Voltage control using coordinated control of Heat Pump Water Heaters with large penetration of photovoltaic systems

It is expected that large amount of photovoltaic (PV) systems will be installed in future power systems. However, introduction of large PV systems create significant problems specially in the distribution system. One of main problems is voltage rise at the end of distribution line due to reverse power flow by the presence of PV systems. In order to mitigate this problem, we propose load control at the customer end. Heat Pump Water Heater (HPWH) has been selected as customer controllable load due its large thermal energy consumption and flexibility in operating time. In this paper, coordinated control of HPWHs is attained based on the node voltages and customer hot water demands. When one of nodes voltage goes closer to maximum allowable voltage or hot water in the tank becomes its minimum level, HPWH is operated in order to avoid voltage rise or hot water shortage. In the voltage control method, primary control priority for operating HPWH is set to maintain reasonable hot water and then set to avoid the voltage rise with intention to keep the participating customers convenience. It is found that proposed voltage control method not only avoids voltage rise but also maintain customer convenience.